Steve. I'll make it simple. At this time in 1972 Drake wanted his 18-34's back. For this he eschewed the normal teenybopper top 40 and played a hipper list. In other words he wasn't programming to your school yard.

You are correct. "I Gotcha" was the first song to hit No. 30 on its descent since "Jumpin' Jack Flash" in 1968. Unfortunately this was a harbinger of things to come. Three more songs did it before the end of 1972. As the song turnover rate decreased in 1973 and beyond, there were a boatload of songs that also did it.